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Debunked: We are headed towards a new ice age

Summary: Professor Zhakarov predicted a “mini ice age” which was reported as far more dramatic than the original idea. It’s just a theory, not established fact. And if it does happen, she predicts a global cooling of 0.1 °C for 30 years. This won’t nearly offset the global warming from human introduced CO2, and indeed it wouldn’t even be enough to halt warming which would just level off for part of that 30 years if he is correct, if we continue to emit CO2 and then at the end would jump up to the expected temperature it would have reached anyway after 30 years.

Another idea is from 1970s that we are headed towards a new ice age some time soon, maybe even this century. That was just based on the average time between ice ages, and assuming that our interglacial (gap between ice ages) was average in length. However the gaps between ice ages vary hugely in length and we now understand why that is. Ours is predicted to be a much longer gap than usual – and the amount of carbon dioxide added to the atmosphere already probably means we won’t get our next ice age for 100,000 years, and possibly not at all for the foreseeable future

IN DETAIL

Profressor Zharkova’s prediction is similar to theMaunder Minimumwhen there were no sunspots and the sun was a bit cooler than usual with the Thames freezing over in London. It’s just a prediction and hypothesis, she’s not saying that the sun has started to cool down yet. Also it’s for a much shorter time than the Maunder minimum.

If we do get a mini ice age of that type – which depends on the sun not on Earth, then the global warming that we’ve had would offset it. But it”s quite a small effect, they say a reduction of average temperatures by 0.1 C, small compared with the global warming of 1 C we’ve had already. Of course local effects could be more than that, that’s global average. Still, don’t expect ice sheets to start advancing. With all the CO2 in the atmosphere, it’s more like a short period of 30 years when maybe the Earth doesn’t warm up quite as much as it would otherwise.

The Sun goes through a sunspot cycle every 11 years. Sometimes has lots of sunspots, sometimes few. And occasionally it goes for decades with no sunspots at all. The last time that happened was several centuries ago. This scientist is predicting it might happen again. But we don’t know if she is right. It is just a theory.

When there are no sunspots, like that, it may be very slightly cooler. So that’s the basis of her prediction that the world might get a cooling of 0.1 C. But the warming from global warming is already around 1 C since pre-industrial. So a cooling of 0.1 C is not going to take us back even to the nineteenth century temperatures never mind the Maunder minimum.

If it does happen it is just a brief pause in warming, not even a cooling. And then three decades later the world would heat up again to whatever temperature it would have been anyway without this brief cooling event.

WAS THE MAUNDER MINIMUM AN ICE AGE

Also there’s some question about whether the Maunder minimum was a global mini ice age or caused by the Sun. It might have been local to Northern Europe. It might also have been caused by volcanoes. It started before the reduction of hot spots.

Oh, is one thing new. On the Maunder minimum, yes it was a sunspot minimum. Yes it was colder in Europe. But that doesn’t mean it was a global reduction in temperature. The reduction in solar intensity was probably no more of a reduction than you get during the 11 years sunspot cycle. The cold period started before the sunspot minimum started. It was not uniformly cold, just on average. Had some very hot summers.

Temperatures in England midlands area – the longest continuous temperature series from a single spot, note these are not global temperatures. Black line is a rolling ten year average. Blue is the year mean. Red and blue lines are max and min for the period. Note that even during the mini ice age period there were occasional very warm years.

It was a time of increased volcanic activity. The correlation with the sunspot minimum is not a strong one due to the onset of colder temperatures before onset of the reduced sunspot numbers. The wikipedia article on the Little Ice Agehas lots of cites and lists of various hypotheses on it which could be worth following up to find out more.

Seems there were cold events in other parts of the world at around the same time, but not necessarily closely correlated with the cold weather in northern Europe. The final effects of it had cleared away by the twentieth century, whatever the cause was.

NO ICE AGE FOR 100,000 YEARS

There is a theory from the 1970s which suggested that there could be an ice age headed our way in the next few thousand years, or sooner -, but that theory is no longer accepted. Even without global warming, the next ice age is expected to be 50,000 years into the future. An Exceptionally Long Interglacial Ahead?

The 1970s theory was simply based on looking at the duration of previous interglacials, which usually last for 10,000 years. They just assumed ours would be the same duration as the previous ones.

Their theory for ice ages back then was based on the idea of a “random walk”. What if the climate just randomly wobbles a bit warmer then a bit colder? And maybe if it shifts a bit warmer by chance, then it has more of a tendency to keep going that way? Then the entire process of moving in and out of the ice ages could be a result of random processes. This isone such paper from 1976. This is a later paper from 1990though by then most climatologists had moved on to new ideas

So the idea was that the climate of the Earth itself was just moving randomly like that. We can predict it short term they thought, but it gets chaotic beyond a few days – and then beyond that, it is just not possible to predict the climate very exactly. Sometimes it gets a bit warmer, sometimes a bit colder, and if it keeps randomly getting colder for long enough we hit an ice age.

The last three interglacials all lasted for about ten thousand years. So, though we couldn’t predict when it could happen and our weather could head towards an ice age at any time, they thought that it would happen at the same time again. Our current Holocene interglacial started 11,700 years ago. So based on that simple argument, it would seem that we are due for another ice age just about now. And that’s how they reasoned back then, seeThe Future of the World’s Climate.

However far from it, the Earth is warming up slightly even without global warming. Back then they didn’t have any detailed theory, as the theory ofMilankovitch cycles which is now accepted widely was only finally established as valid in the late 1970s through study of ice cores (though first put forward as a theory in the 1920s). The ice ages depend on interaction of many different cycles involving slight variations in the Earth’s tilt, how circular the orbit is (eccentricity) and the precession of the equinoxes. SeeMilankovitch Cycles and Glaciation

He found out that the ice ages end at times when we get particularly high levels of sunlight at northerly latitudes.

This is a modern diagram from the NOAA. The warmer interglacials are shown in yellow. The graph at the top in red shows how warm it is in July at 65 degrees North, the modern version of Milankovitch’s curve.

There’s a strong cycle there every 23,000 years due to the precession of the Earth’s axis. Interglacials like the one we are in now happen when the weather is warmer in the northern hemisphere, though not every time. As you see, it has happened every five cycles for the last fifteen cycles.

The bottom line in blue shows the CO2 concentration in the atmosphere which is nowadays thought to play an important role in the warming, though Milankovitch didn’t realize that. (Calculated from bubbles of atmosphere in the Dome Fuji ice core)

The middle line shows the temperature in Antarctica (calculated from hydrogen isotope ratios in the Dome Fuji ice core). The temperature in Antarctica is higher at times when the northern hemisphere gets most sunlight, even though at those times Antarctica gets least sunlight, because of global warming.

This theory was first put forward byMilankovitch. Here he is as a student with a pocket watch.

At best a correlation like that might lead you to consider a hypothesis to investigate further.

Is it a real effect or is it just a coincidence like that? The scientists needed to find out more to check this out. And they did. Though his original explanation wasn’t quite right – carbon dioxide plays more of a role than he realized – his theory once updated with new ideas passed all their tests.

As a result, nowadays, based on a much better understanding of how it works, the scientists predict that ours would be a longer duration interglacial even without global warming, lasting about 50,000 years.

Then, there’s new research that suggests that the next ice age could be postponed from 50,000 to 100,000 years in the future due to the effects of the CO2. See: Fossil fuel burning ‘postponing next ice ageYou can click through the link in that article to get to the nature paper itself complete under their sharing initiative.

The authors selected only the models that most accurately tracked the previous ice ages, and used that to study whether or not we are due to plunge into the next ice age. They found that if they ran the models with CO2 levels of 240 ppm, similar to the Halocene (the previous interglacial, last time the world was this warm), then the next ice age would be as soon as 1500 years into the future.

But if they used the pre-industrial levels of CO2 of 280 ppm, then the next ice ages should be 50,000 and 90,000 years from now (with a possibility of a slowly approaching ice age 20,000 years from now). Just that extra 40 ppm made all the difference. They are unsure why we had more CO2 this time around. Perhaps human activity even in pre-industrial society was enough to raise the levels by 40 ppm, which isn’t very much, or at least contributed to the levels.

They found that with 500 Gt of emissions, not far off what we have already reached, we may already have enough CO2 in the atmosphere to make a difference to the ice sheets over thousands of years. If it reaches 1000 GT then the chance of an ice age in the next 100,000 years is notably reduced and with 1500 GT of emissions then it is very unlikely that we get an ice age in the next 100,000 years. And with higher levels of emissions, then we will end the pattern of ice ages altogether. You can read it in full under Nature’s sharing initiative if you click on the link ” published in the journal Nature” in the article in the Guardian here:Fossil fuel burning ‘postponing next ice age

In that paper, they say

” Using an ensemble of simulations generated by an Earth system model of intermediate complexity constrained by palaeoclimatic data, we suggest that glacial inception was narrowly missed before the beginning of the Industrial Revolution. The missed inception can be accounted for by the combined effect of relatively high late-Holocene CO2 concentrations and the low orbital eccentricity of the Earth7. Additionally, our analysis suggests that even in the absence of human perturbations no substantial build-up of ice sheets would occur within the next several thousand years and that the current interglacial would probably last for another 50,000 years.”

So in other words yes, we were due to go into an ice age around the start of the industrial Revolution, but it’s not just the CO2 that stopped it. The various cycles are complex with many factors interacting and their analysis suggests that this time around the interglacial would have lasted 50,000 years anyway.

Their crucial graph is this one on page 203 of the paper.

The graph at the top shows the effects of different levels of CO2 now over the next 100,000 years plus in black, variations in amount of sunlight. The graph at the bottom shows the amount of ice in red, orange or blue with the colour there matched to the colour of the curve in the top half of the graph.

Notice that there’s a significant difference between the predictions of the amount of ice, depending on the levels we reach in the near future, even 100,000 years from now.

With all the scenarios, there is much less CO2 of course 100,000 years in the future, but you still see differences because the amount you have then if we get to 1000 gigatons this century is still double the amount you get if we don’t go above 500 gigatons. Apparently even that small amount of CO2 is enough to be significant. The reason is that the way carbon dioxide behaves in the atmosphere is very complex.

The average lifetime of a CO2 molecule is around 4 years in the atmosphere. But that’s for the more rapid processes such as plant growth, and absorption in the surface water of the ocean. Much of that gets circulated back into the atmosphere again.

The slower cycle of removal of CO2 from the atmosphere is complex and behaves in surprising ways.

So for example, of the roughly 32 billion tons of CO2 that humans added to the atmosphere in 2010

16 billion tons will still be there 50 years later, in 2060,

8 billion tons will still be there 250 years later in 2260

4.8 billion tons will still be there indefinitely, for thousands of years.

That 15% which is left after thousands of years with a long term half life of 13,500 years is enough to prevent the next ice age and possibly, depending how much CO2 we add in total, end the cycle of ice ages altogether.

That of course is not necessarily a bad thing. The climate is much more stable between ice ages. During an ice age much of the world is covered in ice and can’t be cultivated and the climate also varies very rapidly over time periods of decades. The main problem with global warming is not that it is making Earth a bit warmer, it’s just the speed of the change. And that’s not a doomsday scenario either.